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Heavy flavor production at RHIC

This article discusses the measurement of heavy flavor production at RHIC, including total cross-sections, related differential cross-sections, RAA, flow, charm/bottom ratio, and results at higher energy. The article also explores the methods used to obtain these results and addresses a question regarding detector thickness variation.

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Heavy flavor production at RHIC

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  1. Heavy flavor production at RHIC Yonsei Univ. Y. Kwon

  2. Contents • Introduction • Current measurements • Total cross sections by PHENIX and STAR • Related differential cross sections • RAA, flow, and further results • Charm/Bottom ratio • How do we obtain the result? • Direct reconstruction • Non-photonic e & prompt  • Results at higher energy • A question?

  3. parton light medium Introduction : heavy quarks as a probe p+p : pQCD test baseline for A+A A+A : flow thermalization high pT suppression energy loss ENERGY LOSS 3

  4. Introduction : (open) heavy flavor measurement Direct: reconstruction of all decay products Indirect: charm and beauty viaelectrons • c  e+ + anything (B.R.: 9.6%) • b  e+ + anything (B.R.: 10.9%) • issue of photonic background charm (and beauty) viamuons • c  + + anything (B.R.: 9.5%)

  5. Total cross sections,PHENIX vs STAR Binary scaling STAR results ~ 2 times larger than PHENIX

  6. Forward prompt - production (PHENIX) PPG057 : PRD76, 092992(2007)

  7. Leptons from Heavy flavor, PHENIX PRL, 98, 172301 (2007) PHENIX Preliminary p+p 200GeV/c Systematically higher than FONLL calculation e yield shows binary scaling, high pT suppression in central Au+Au

  8. Leptons from heavy flavor, STAR STAR Preliminary • Combined fit of , D0, low pT e • Low pT muon constrains charm cross-section 8

  9. c dominant b dominant Heavy quarks in p+p from e+e- at PHENIX

  10. RAA STAR hadrons pT> 6 GeV/c d+Au: no suppression expected  slight enhancement expected (Cronin effect) Peripheral Au+Au: no suppression expected Central Au+Au: less suppression expected ? Semi-Central Au+Au: very little suppression expected Nuclear modification factor

  11. Energy Loss?

  12. Elliptic flow v2 – NPE from HF decays PHENIX RUN4 : PRL, 98, 172301 (2007)

  13. How do we obtain the result?

  14. Direct D-meson reconstruction (STAR) D0 Phys. Rev. Lett. 94 (2005) STAR Preliminary No displaced vertex used

  15. Mostly from heavy quark Direct measurement : converter method Estimation based on other (PHENIX) measurement : Cocktail method Non-photonic electrons Inclusive electrons = photonic + non-photonic electron Dominant background : 0 Dalitz decay,  conversion

  16. -measurement, sources Collision 2 1 3 4 5 1 : Hadrons, interacting and absorbed (98%), 2 : Charged /K's,“decaying into ”before absorber (≤1%), 3: Hadrons, penetrating and interacting(“stopped”) 4 : Hadrons, “punch-through”, 5 : Prompt ,”desiredsignal” Tracker Absorber Identifier Collision vertex range Symbols Hadron Detector Absorber Muon

  17. PRELIMINARY -measurement, Signal composition Generator ( Decay  + punch-through ) 1. Light hadron measurement by PHENIX central arm (y = 0) 2. Gaussian extrapolation in rapidity to muon arm acceptance ( = 2.5) 3. Simplified spectrometer geometry.

  18. Forward prompt - production (PHENIX) PPG057 : PRD76, 092992(2007)

  19. Leptons from heavy flavor, PHENIX PRL, 98, 172301 (2007) PHENIX Preliminary p+p 200GeV/c Systematically higher than FONLL calculation Integral e yield follows binary scaling, strong high pT suppression at central AuAu collisions

  20. Leptons from heavy flavor, STAR STAR Preliminary • Combined fit of , D0, low pT e • Low pT muon constrains charm cross-section 20

  21. STAR high pT non-photonic electrons STAR High pTelectrons (EMC trigger) FONLL* 5 p+p spectra Phys. Rev. Lett. 98 (2007) 192301

  22. Bottom contribution to non-photonic e (be)/(ce+be) Data consistent with FONLL.

  23. Results at higher energy

  24. Differential charm cross section

  25. Differential bottom cross section

  26. A question? • STAR high pT electrons? • If it’s problem, normalization (efficiency)? • Detector thickness must be varying a lot!

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